Most older Americans are troubled by low-level depression or sleep disturbances, which are often intimately intertwined. In the first 5 years of AG12364, they have been examining the etiologies of depression and insomnia in aging volunteers. Their findings suggest an appalling degree of circadian malsynchronization among aging Americans, which possibly explains part of their insomnia and low mood. Further, their volunteers displayed surprisingly weak circadian and clinical responses to 4 days of bright light treatment, indicating possible light resistance. In this renewal, they will test more extended 4-week bright light treatments in the home, to determine if light resistance in volunteers ages 60-79 years can be overcome with a longer duration of treatment. One hundred fifty volunteers with significant depressive complaints will be recruited for a trial consisting of one-week placebo baseline terminating in a half-night sleep deprivation, followed by 4 weeks randomized assignment to 10,000 lux white light or 10 lux red light placebo. Phase-typing during baseline will determine before randomization whether treatment should best be given in the morning, mid-day, or evening. Fractional urine samples for 6-sulphatoxymelatonin will be collected for 48 hours at the end of baseline and for 48 hours at the end of the randomized treatment, to determine if 10,000 lux treatments successfully normalize malsynchronized circadian phase adjustments. The success of the treatment in lowering the GDS depression score and in reducing sleep complaints will be examined.